The invention relates generally to power-driven conveyors and, more particularly, to hinge rod retention structure in plastic conveyor belts constructed of rows of modules pivotally interconnected by hinge rods.
Conventional modular plastic conveyor belts and chains are constructed of modular plastic links, or belt modules, arranged end to end and side to side in rows. Spaced-apart hinge eyes extending from each end of the modules include aligned rod apertures. The hinge eyes along the leading end of a row of modules are interleaved with the hinge eyes along the trailing end of an adjacent row. Hinge rods, residing in the aligned rod apertures of interleaved hinge eyes, connect adjacent rows together end to end to form a conveyor belt of selected length and width capable of articulating about a drive sprocket or drum at the hinges formed between adjacent belt rows.
But belt motion and belt tension, especially in an environment subjected to wide temperature excursions, can cause the hinge rods to migrate along the hinge or to lengthen relative to the width of the belt. If a rod migrates away from one side of the belt, the modules at that side can disengage, which can cause damage to the belt. If a rod is allowed to extend out of the hinge beyond the side of the belt, the rod can catch on conveyor structure or other objects and cause damage. Consequently, it is important that hinge rods be contained within the belt.
Some conventional modular plastic conveyor belts use a stop in the form of a thin strip molded integrally as part of an edge module of a modular belt to retain a hinge rod in the belt. The integrally-molded stop and edge module are both made of the same material. But some applications require that the module exhibit properties, such as flexibility or stiffness, that are inconsistent with forming a firm, but resilient stop that can elastically bend from a blocking position preventing a hinge rod from migrating past the side edge of the belt to a non-blocking position during insertion of a hinge rod into a rod aperture in the belt.
Consequently, there is a need for a rod retention system for a modular plastic conveyor belt whose effectiveness does not depend on the material out of which the belt is molded.